Fix couple problems with in-body incremental resolution.

pkg/analyzer/lib/src/task/dart.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer.src.task.dart;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 957 matching lines @@
 /**
  * A list of the [AnalysisError]s reported while resolving static
  * [INFERABLE_STATIC_VARIABLES_IN_UNIT] defined in a unit.
  *
  * The result is only available for [LibrarySpecificUnit]s, and only when strong
  * mode is enabled.
  */
 final ListResultDescriptor<AnalysisError>
     STATIC_VARIABLE_RESOLUTION_ERRORS_IN_UNIT =
     new ListResultDescriptor<AnalysisError>(
-        'STATIC_VARIABLE_RESOLUTION_ERRORS_IN_UNIT', null);
+        'STATIC_VARIABLE_RESOLUTION_ERRORS_IN_UNIT', AnalysisError.NO_ERRORS);
 
 /**
  * The additional strong mode errors produced while verifying a
  * compilation unit.
  *
  * The list will be empty if there were no errors, but will not be `null`.
  *
  * The result is only available for [LibrarySpecificUnits]s representing a
  * compilation unit.
  *
@@ skipping 1660 matching lines @@
       return false;
     }
     return addChangedElements(referencedNames, targetLibrary);
   }
 
   @override
   void gatherEnd() {
     currentVisitUnits.clear();
   }
 
+  @override
+  bool gatherRequired() {
+    return true;
+  }
+
   bool hasAffectedHintsVerifyErrors(
       ReferencedNames references, Source refLibrary) {
     for (String superName in references.superToSubs.keys) {
       if (isChangedOrClass(refLibrary, superName)) {
         _log(() => '$refLibrary hints/verify errors are affected because '
             '${references.superToSubs[superName]} subclasses $superName');
         return true;
       }
     }
     for (String name in references.names) {
@@ skipping 3998 matching lines @@
 
   @override
   bool moveNext() {
     if (_newSources.isEmpty) {
       return false;
     }
     currentTarget = _newSources.removeLast();
     return true;
   }
 }